| Internet-Draft | MIMI Message ID in AAD | April 2025 |
| Mahy | Expires 24 October 2025 | [Page] |
The More Instant Messaging Interoperability (MIMI) content format defines a MIMI Message ID, communicated only to members of the Messaging Layer Security (MLS) group in which the message was sent. This document defines a way to share a Message ID in the MLS Additional Authenticated Data (AAD) so it is visible to MIMI providers.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://rohanmahy.github.io/mimi-msgid-aad/draft-mahy-mimi-msgid-aad.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-mahy-mimi-msgid-aad/.¶
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Many messaging protocols and formats have a Message ID. The MIMI content format defines how to calculate a MIMI Message ID Section 3.3 of [I-D.ietf-mimi-content] for an application message. A MIMI Message ID is currently only shared end-to-end encrypted with members of the MLS [RFC9420] group in which the message was sent. This document defines an optional mechanism to share a Message ID in the MLS AAD, so it is visible to intermediary providers. This greatly facilitates debugging and troubleshooting, but causes a modest reduction in privacy.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
This document defines a new Safe AAD message_id component as described in Section 4.9 of [I-D.ietf-mls-extensions].¶
When the content of an MLS application message is a MIMI content message (media type application/mimi-content), if the message_id component is present inside SafeAAD.aad_items, it MUST contain the MIMI content Message ID calculated as described in Section 3.3 of [I-D.ietf-mimi-content].¶
To the extent that other application formats or media types have a Message ID, the Message ID for an application message of that type or format MAY be conveyed in this extension.¶
An attacker with access to a fragment of message history, and the message logs of a MIMI provider in the path of a message could potentially learn more about the participants of a particular MIMI room or the room's corresponding MLS group.¶
TODO acknowledge.¶